Study: Household Dust Is Main Source Of Flame Retardants In Humans

Jul 01, 2005

Household dust is the main route of exposure to flame retardants for people -- from toddlers to adults -- followed by eating animal and dairy products, according to a report in the July 15 issue of the American Chemical Society's journal Environmental Science & Technology. Until this study, which is based on a computer model developed by Canadian researchers, scientists have been unsure exactly how people are being exposed.

Polybrominated diphenylethers (PBDEs) -- used widely as flame-retardant additives in electronics and furniture -- have been detected in humans across the globe, with especially high levels in North America. Little is known about the specific toxic effects of brominated flame retardants, but some researchers say that the increasing presence of the compounds in human tissue is cause for concern because they have been associated with cancer and other health problems in animal studies.

"Our work is good news and bad news," said Miriam Diamond, PhD, the study's lead author and an environmental chemist at the University of Toronto. "Good news because we've identified the main route of exposure to PBDEs -- house dust; bad news because we need more action to remove PBDEs from household products and replace them with alternatives that are effective in reducing hazards related to fires and that do not accumulate in the environment."

PBDEs are released into the environment at their manufacturing sources and also through everyday product wear and tear, which is the presumed source of the chemicals in house dust, according to Diamond. Asked if drinking water could be a possible source, Diamond said: "No, it's not a significant route of exposure."

A small study published earlier this year in ES&T found PBDEs in the dust of 16 homes tested in the Washington, D.C., area and one home in Charleston, S.C. The work of Diamond and her co-authors builds on that research with a more complete analysis of all potential exposure pathways, including food, soil, dust and inhalation of indoor and outdoor air. Using a combination of measured concentrations and computer modeling, she and her coworkers estimated the emissions and fate of PBDEs in the Toronto area.

Toddlers tend to have high levels of PBDEs, which is most likely because they are frequently bringing toys and other objects from the floor to their mouths, the researchers suggest. Breast-feeding infants have higher levels of PBDEs than all other ages, which is consistent with earlier research revealing high levels of PBDEs in the breast milk of women across North America.

"We hypothesize that women with very high PBDE concentrations in breast milk may be super-exposed," Diamond says. "Given evidence from the literature, it seems likely that if one reduces one's exposure, then presumably the breast milk concentrations will fall."

Diamond suggests a number of steps that people can take to minimize exposure, such as frequent house cleaning and improved ventilation. "It seems to me that any measures one takes to minimize dust will reduce exposures," she said.

Officials in the United States and Canada are still debating the fate of flame retardants, although the main U.S. manufacturer has discontinued production of two types of PBDEs -- the penta and octa formulations -- as part of a voluntary agreement with EPA. The European Union has banned the penta and octa formulations and is currently considering a voluntary phase-out and further study on a third type, the deca formulation.